玩转Google开源C++单元测试框架Google Test系列(gtest)之二 - 断言

原文地址：http://www.cnblogs.com/coderzh/archive/2009/04/06/1430364.html

一、前言

这篇文章主要总结gtest中的所有断言相关的宏。 gtest中，断言的宏可以理解为分为两类，一类是ASSERT系列，一类是EXPECT系列。一个直观的解释就是：

1. ASSERT_* 系列的断言，当检查点失败时，退出当前函数（注意：并非退出当前案例）。

2. EXPECT_* 系列的断言，当检查点失败时，继续往下执行。

二、示例

<!-- <br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />--> // int型比较，预期值：3，实际值：Add(1,2)
EXPECT_EQ( 3 ,Add( 1 , 2 ))
//

假如你的Add(1, 2) 结果为4的话，会在结果中输出：

<!-- <br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />--> g:/myproject/c ++ /gtestdemo/gtestdemo/gtestdemo.cpp( 16 ):error:Valueof:Add( 1 , 2 )
Actual: 4
Expected: 3

如果是将结果输出到xml里的话，将输出：（关于将结果输出为xml，见：http://www.cnblogs.com/coderzh/archive/2009/04/10/1432789.html ）

<!-- <br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />--> < testcase name ="Demo" status ="run" time ="0" classname ="AddTest" >
< failure message ="Valueof:Add(1,2) Actual: 4 Expected: 3" type ="" > <![CDATA[ g:/myproject/c++/gtestdemo/gtestdemo/gtestdemo.cpp:16
Valueof:Add(1,2)
Actual: 4
Expected: 3 ]]> </ failure >
</ testcase >

如果你对自动输出的出错信息不满意的话，你还可以通过操作符<<将一些自定义的信息输出，通常，这对于调试或是对一些检查点的补充说明来说，非常有用！

下面举个例子：

如果不使用<<操作符自定义输出的话：

<!-- <br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />--> for ( int i = 0 ;i < x.size(); ++ i)
{
EXPECT_EQ(x[i],y[i]) ;
}

看到的结果将是这样的，你根本不知道出错时 i 等于几：

<!-- <br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />--> g:/myproject/c ++ /gtestdemo/gtestdemo/gtestdemo.cpp( 25 ):error:Valueof:y[i]
Actual: 4
Expected:x[i]
Which is : 3

如果使用<<操作符将一些重要信息输出的话：

<!-- <br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />--> for ( int i = 0 ;i < x.size(); ++ i)
{
EXPECT_EQ(x[i],y[i]) << " Vectorsxandydifferatindex " << i;
}

从输出结果中就可以定位到在 i = 2 时出现了错误。这样的输出结果看起来更加有用，容易理解：

<!-- <br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />--> g:/myproject/c ++ /gtestdemo/gtestdemo/gtestdemo.cpp( 25 ):error:Valueof:y[i]
Actual: 4
Expected:x[i]
Which is : 3
Vectorsxandydifferatindex 2

三、布尔值检查

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_TRUE( condition ) ;	EXPECT_TRUE( condition ) ;	condition is true
ASSERT_FALSE( condition ) ;	EXPECT_FALSE( condition ) ;	condition is false

四、数值型数据检查

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_EQ( expected , actual );	EXPECT_EQ( expected , actual );	expected == actual
ASSERT_NE( val1 , val2 );	EXPECT_NE( val1 , val2 );	val1 != val2
ASSERT_LT( val1 , val2 );	EXPECT_LT( val1 , val2 );	val1 < val2
ASSERT_LE( val1 , val2 );	EXPECT_LE( val1 , val2 );	val1 <= val2
ASSERT_GT( val1 , val2 );	EXPECT_GT( val1 , val2 );	val1 > val2
ASSERT_GE( val1 , val2 );	EXPECT_GE( val1 , val2 );	val1 >= val2

五、字符串检查

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_STREQ( expected_str , actual_str );	EXPECT_STREQ( expected_str , actual_str );	the two C strings have the same content
ASSERT_STRNE( str1 , str2 );	EXPECT_STRNE( str1 , str2 );	the two C strings have different content
ASSERT_STRCASEEQ( expected_str , actual_str );	EXPECT_STRCASEEQ( expected_str , actual_str );	the two C strings have the same content, ignoring case
ASSERT_STRCASENE( str1 , str2 );	EXPECT_STRCASENE( str1 , str2 );	the two C strings have different content, ignoring case

*STREQ*和*STRNE*同时支持char*和wchar_t* 类型的，*STRCASEEQ*和*STRCASENE*却只接收char*，估计是不常用吧。下面是几个例子：

<!-- <br /> <br /> Code highlighting produced by Actipro CodeHighlighter (freeware)<br /> http://www.CodeHighlighter.com/<br /> <br /> --> TEST(StringCmpTest,Demo)
{
char * pszCoderZh = " CoderZh " ;
wchar_t * wszCoderZh = L " CoderZh " ;
std:: string strCoderZh = " CoderZh " ;
std::wstringwstrCoderZh = L " CoderZh " ;

EXPECT_STREQ( " CoderZh " ,pszCoderZh);
EXPECT_STREQ(L " CoderZh " ,wszCoderZh);

EXPECT_STRNE( " CnBlogs " ,pszCoderZh);
EXPECT_STRNE(L " CnBlogs " ,wszCoderZh);

EXPECT_STRCASEEQ( " coderzh " ,pszCoderZh);
// EXPECT_STRCASEEQ(L"coderzh",wszCoderZh);不支持

EXPECT_STREQ( " CoderZh " ,strCoderZh.c_str());
EXPECT_STREQ(L " CoderZh " ,wstrCoderZh.c_str());
}

六、显示返回成功或失败

直接返回成功：SUCCEED();

返回失败：

Fatal assertion	Nonfatal assertion
FAIL();	ADD_FAILURE();

<!-- <br /> <br /> Code highlighting produced by Actipro CodeHighlighter (freeware)<br /> http://www.CodeHighlighter.com/<br /> <br /> --> TEST(ExplicitTest,Demo)
{
ADD_FAILURE() << " Sorry " ; // NoneFatalAsserton，继续往下执行。

// FAIL(); // FatalAssertion，不往下执行该案例。

SUCCEED();
}

七、异常检查

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_THROW( statement , exception_type );	EXPECT_THROW( statement , exception_type );	statement throws an exception of the given type
ASSERT_ANY_THROW( statement );	EXPECT_ANY_THROW( statement );	statement throws an exception of any type
ASSERT_NO_THROW( statement );	EXPECT_NO_THROW( statement );	statement doesn't throw any exception

例如：

<!-- <br /> <br /> Code highlighting produced by Actipro CodeHighlighter (freeware)<br /> http://www.CodeHighlighter.com/<br /> <br /> --> int Foo( int a, int b)
{
if (a == 0 || b == 0 )
{
throw " don'tdothat " ;
}
int c = a % b;
if (c == 0 )
return b;
return Foo(b,c);
}

TEST(FooTest,HandleZeroInput)
{
EXPECT_ANY_THROW(Foo( 10 , 0 ));
EXPECT_THROW(Foo( 0 , 5 ), char * );
}

八、Predicate Assertions

在使用EXPECT_TRUE或ASSERT_TRUE时，有时希望能够输出更加详细的信息，比如检查一个函数的返回值TRUE还是FALSE时，希望能够输出传入的参数是什么，以便失败后好跟踪。因此提供了如下的断言：

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_PRED1( pred1, val1 );	EXPECT_PRED1( pred1, val1 );	pred1(val1) returns true
ASSERT_PRED2( pred2, val1, val2 );	EXPECT_PRED2( pred2, val1, val2 );	pred2(val1, val2) returns true
...	...	...

Google人说了，他们只提供<=5个参数的，如果需要测试更多的参数，直接告诉他们。下面看看这个东西怎么用。

<!-- <br /> <br /> Code highlighting produced by Actipro CodeHighlighter (freeware)<br /> http://www.CodeHighlighter.com/<br /> <br /> --> bool MutuallyPrime( int m, int n)
{
return Foo(m,n) > 1 ;
}

TEST(PredicateAssertionTest,Demo)
{
int m = 5 ,n = 6 ;
EXPECT_PRED2(MutuallyPrime,m,n);
}

当失败时，返回错误信息：

error: MutuallyPrime(m, n) evaluates to false, where
m evaluates to 5
n evaluates to 6

如果对这样的输出不满意的话，还可以自定义输出格式，通过如下：

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_PRED_FORMAT1( pred_format1, val1 );`	EXPECT_PRED_FORMAT1( pred_format1, val1 );	pred_format1(val1) is successful
ASSERT_PRED_FORMAT2( pred_format2, val1, val2 );	EXPECT_PRED_FORMAT2( pred_format2, val1, val2 );	pred_format2(val1, val2) is successful
...	...

用法示例：

<!-- <br /> <br /> Code highlighting produced by Actipro CodeHighlighter (freeware)<br /> http://www.CodeHighlighter.com/<br /> <br /> --> testing::AssertionResultAssertFoo( const char * m_expr, const char * n_expr, const char * k_expr, int m, int n, int k){
if (Foo(m,n) == k)
return testing::AssertionSuccess();
testing::Messagemsg;
msg << m_expr << " 和 " << n_expr << " 的最大公约数应该是： " << Foo(m,n) << " 而不是： " << k_expr;
return testing::AssertionFailure(msg);
}

TEST(AssertFooTest,HandleFail)
{
EXPECT_PRED_FORMAT3(AssertFoo, 3 , 6 , 2 );
}

失败时，输出信息：

error: 3 和 6 的最大公约数应该是：3 而不是：2

是不是更温馨呢，呵呵。

九、浮点型检查

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_FLOAT_EQ( expected, actual );	EXPECT_FLOAT_EQ( expected, actual );	the two float values are almost equal
ASSERT_DOUBLE_EQ( expected, actual );	EXPECT_DOUBLE_EQ( expected, actual );	the two double values are almost equal

对相近的两个数比较：

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_NEAR( val1, val2, abs_error );	EXPECT_NEAR (val1, val2, abs_error );	the difference between val1 and val2 doesn't exceed the given absolute error

同时，还可以使用：

<!-- <br /> <br /> Code highlighting produced by Actipro CodeHighlighter (freeware)<br /> http://www.CodeHighlighter.com/<br /> <br /> --> EXPECT_PRED_FORMAT2(testing::FloatLE,val1,val2);
EXPECT_PRED_FORMAT2(testing::DoubleLE,val1,val2);

十、Windows HRESULT assertions

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_HRESULT_SUCCEEDED( expression );	EXPECT_HRESULT_SUCCEEDED( expression );	expression is a success HRESULT
ASSERT_HRESULT_FAILED( expression );	EXPECT_HRESULT_FAILED( expression );	expression is a failure HRESULT

例如：

<!-- <br /> <br /> Code highlighting produced by Actipro CodeHighlighter (freeware)<br /> http://www.CodeHighlighter.com/<br /> <br /> --> CComPtrshell;
ASSERT_HRESULT_SUCCEEDED(shell.CoCreateInstance(L " Shell.Application " ));
CComVariantempty;
ASSERT_HRESULT_SUCCEEDED(shell -> ShellExecute(CComBSTR(url),empty,empty,empty,empty));

十一、类型检查

类型检查失败时，直接导致代码编不过，难得用处就在这？看下面的例子：

<!-- <br /> <br /> Code highlighting produced by Actipro CodeHighlighter (freeware)<br /> http://www.CodeHighlighter.com/<br /> <br /> --> template < typenameT > class FooType{
public :
void Bar(){testing::StaticAssertTypeEq < int ,T > ();}
};

TEST(TypeAssertionTest,Demo)
{
FooType < bool > fooType;
fooType.Bar();
}

十二、总结

本篇将常用的断言都介绍了一遍，内容比较多，有些还是很有用的。要真的到写案例的时候，也行只是一两种是最常用的，现在时知道有这么多种选择，以后才方便查询。